The present invention relates to an immunoassay for estrogens, especially 17xcex2-estradiol and estrone, and to a labeled compound used in the immunoassay.
Estrogens are a representative example of steroid hormones (female sex hormones). Over ten kinds of compounds are currently known as estrogens. Estrogens are metabolized into stable estradiols in human blood like other female sex hormones. The estradiols are mainly excreted as urine and diffused into the environment such as into river water, lake water, seawater, waste water, soil, etc.
Estrogens have drawn attention because of the problem of feminization in humans, domestic animals, fish, etc. For example, 17-estradiol reacts with estrogen receptors. The avidity of the estradiol to the receptors is 1,000 to 10,000 times as high as the avidity of bisphenol A, nonylphenol, alkyl phthalates and the like which are now recognized as environmental hormones causing problems.
17xcex2-estradiol and estrone have conventionally been measured by immunoassays such as radioimmunoassay and enzyme immunoassay. These immunoassays are known as techniques for measuring female sex hormones in human blood.
The immunoassays which were originally developed for the detection and measurement of female sex hormones in blood, however, remain unsatisfactory with respect to sensitivity, etc., when used for the detection and measurement of estrogens in environments such as river water, lake water, seawater, waste water and soil.
An object of the present invention is to solve the above problem of the prior art and provide a highly sensitive immunoassay system for estrogens.
The present inventors carried out intensive research and found that when a novel biotinylated estradiol derivative of the formula (1) shown below is utilized as a labeled compound in the immunoassay system for estrogens, a highly sensitive system for the detection and measurement of estrogens can be created. The present invention has been achieved based on this novel finding.
The present invention provides a biotinylated estradiol derivative represented by the formula (1) 
wherein one of R1 and R2 is an hydrogen atom and the other is a group represented by 
wherein R3s are the same or different and represent an arginine residue or a lysine residue, x is 0 or 1, y is an integer from 1 to 5, and z is an integer from 1 to 3. The derivative represented by formula (1) is hereinafter referred to as xe2x80x9ccompound (1)xe2x80x9d.
Particularly, the present invention provides the biotinylated estradiol derivative wherein R1 is a hydrogen atom, R3 is an arginine residue, X is 1, Y is 2 and Z is 2, and the biotinylated estradiol derivative wherein R2 is a hydrogen atom, R3 is an arginine residue, X is 0, Y is 1, and Z is 2.
Further, the present invention provides an immunoassay system for estrogens which utilizes compound (1) as a labeled compound, particularly the immunoassay system for 17xcex2-estradiol and estrone.